1. Field of the Invention
This invention relates to helicopters and more particularly to an analog mixer to be used in the control system of a helicopter rotor to vary the phase angle thereof in flight as a function of helicopter speed.
2. Description of the Prior Art
The only known prior art relative to the variation of helicopter rotor phase angle in flight is Girard U.S. Pat. No. 3,146,970 in which helicopter phase angle is varied in flight but not as a function of helicopter speed and not such as to achieve decoupling between phase angle variation and control output. Cheney U.S. Pat. No. 3,521,971 directs itself to the use of phase angle in helicopters, but not variable phase angle as a function of helicopter speed.
It has been known for some time that there are advantages to be gained by using counterrotating rigid rotors, however, the control of such rotors presented problems which had to be overcome to optimize performance and controllability. It has now been determined that this can be accomplished by varying rotor phase angle in flight as a function of helicopter forward speed. My analog mixer taught herein accomplishes that function efficiently, with minimal mechanical complication, with high reliability and without imparting any rotor control inputs to the rotor control system during the phase angle varying operation.